Thermal ink drop on demand devices on a single chip with vertical integration of driver device

Abstract

This application discloses a novel method to integrate thermal drop on demand ink jet devices and related pulse driver circuitry for chips used in thermal ink jet printers. This integrated printhead chip is made by first fabricating on the substrate the driver pulse circuitry through the last level of metallization. Once complete, a low temperature (<400 C.) CVD oxide is deposited and planarized. It is of sufficient thickness (3 to 4 microns) to insure a good thermal barrier between the pulse circuitry and the thermal inkjet devices. After planarization, the resistor material is deposited and patterned. Openings are then patterned to the inputs and outputs of the pulse driver circuitry. Aluminum copper metallurgy is deposited and patterned to connect the resistor to the pulse driver output and define the heater resistor areas. Inorganic and organic barrier layers are applied and patterned to protect the resistor material and interconnecting metallurgy from the corrosive effects of the ink. After testing, ink holes are drilled and the wafer is diced and nozzle plates are attached to the chips. Thus, this "on chip" driver integration enables the pulse driver circuitry to be moved to the thermal ink jet printhead. It offers advantages over other methods of ink jet/driver device integration by the chip footprint the same without decreasing the dimensions of the respective devices.

We claim: 
     
       1. A vertically integrated thermal ink jet printhead comprising: an pulse driver device disposed on a semiconductor substrate;   a planarized thermal barrier layer disposed on said pulse driver device;   a thermal ink jet device disposed on said planarized thermal barrier layer at least a portion of which is disposed directly over said pulse driver device; and,   a conducting material which electrically connects said pulse driver device with said thermal ink jet device through said planarized thermal barrier layer.   
     
     
       2. The printhead as recited in claim 1 wherein said thermal ink jet device comprises: a heater area composed of a resistor material which heats ink stored in an ink reservoir disposed over said thermal ink jet device;   a conducting material which abuts said heater area and conducts electrical current from said pulse driver device; and,   a protective layer disposed over said heater area and said conducting material.   
     
     
       3. A vertically integrated thermal ink jet printhead comprising: a set of pulse driver devices disposed on a semiconductor substrate;   a planarized thermal barrier layer disposed on said set of pulse driver devices;   a set of thermal ink jet devices disposed on said planarized thermal barrier layer at least a portion of which are disposed directly over said pulse driver devices; and,   a patterned conductive material which electrically connects a respective one of said set of pulse drive devices with a respective one of said set of thermal ink jet devices through said thermal barrier layer.   
     
     
       4. The printhead as recited in claim 3, wherein said thermal barrier layer is a CVD silicon oxide layer. 
     
     
       5. The printhead as recited in claim 3, wherein said thermal ink jet device comprises a heater region composed of a resistor material defined by said conductive material which electrically connects said thermal ink jet device to said pulse driver device. 
     
     
       6. The printhead a recited in claim 5, wherein said resistor material is selected from the group consisting of hafnium diboride, and tantalum aluminide. 
     
     
       7. The printhead as recited in claim 3, wherein the thermal ink jet device further comprises a protective layer to protect said printhead from corrosion. 
     
     
       8. The printhead as recited in claim 3, wherein the protective layer comprises a layer of silicon nitride and a layer of silicon carbide.